AADT turns up on traffic management plans, permit applications, pavement designs and road safety reports. It's the standard measure of how busy a road is. This guide explains what the number means, how the Department of Transport and Main Roads (TMR) counts it on Queensland's state-controlled roads, how to read the extra detail that comes with it, and how traffic management uses it.
AADT in one sentence
AADT, annual average daily traffic, is the number of vehicles that pass a point on a road in a day, averaged over a whole year. A road with an AADT of 12,000 carries 12,000 vehicles on an average day, counting both directions unless the figure says otherwise.
Because it's a yearly average, it smooths out the difference between weekdays and weekends, school holidays and the wet season. Traffic on a particular day or hour can be much higher or lower, which is why the hourly figures that come with it matter just as much (see below).
You'll also see ADT, average daily traffic, which is the average over the days actually counted. AADT is ADT adjusted to stand for the whole year.
How TMR counts traffic
TMR counts traffic at more than 2,000 sites on the state-controlled network and publishes the results as its traffic census on the Queensland Open Data Portal. There are two kinds of site:
- Permanent sites count all year round with equipment built into the road.
- Coverage (short-term) sites are counted for a short period, typically a few days to a week, every few years, with portable counters such as tubes across the road. Their counts are seasonally adjusted to estimate a whole year.
In the years between counts, TMR estimates each coverage site's AADT from its last count and the growth seen elsewhere. The census records both the year a figure is for and the year it was actually collected, so you can tell a fresh count from an estimate: a 2025 figure collected in 2019 is an estimate based on a six-year-old count.
Each site's count stands for a stretch of road, called a segment, from one through distance (chainage) to another on the same road section. On a long rural highway that can be over 100 km: the Mulligan Highway between about 12.75 km and 144.47 km of section 34B takes its figure from one permanent counter near Lakeland.
Reading the detail: direction, heavy vehicles and classes
Direction
The census gives AADT for both directions together and for each direction separately: with gazettal (the road's official direction, in which chainage increases) and against gazettal. On a divided road, each carriageway carries one direction. At the Bruce Highway count site near Yandina, for example, 2025's 41,565 vehicles a day were 20,646 with gazettal and 20,919 against.
Heavy vehicles
The heavy vehicle percentage is the share of traffic in Austroads vehicle classes 3 to 12: trucks, buses and combinations. It varies a lot between roads and even directions. A freight route can be a quarter or a third heavy vehicles, while a commuter road may be well under ten per cent.
Vehicle classes
Classified counts break traffic into the 12 Austroads vehicle classes, which TMR also groups into four:
| Group | Austroads classes | Vehicles |
|---|---|---|
| Light vehicles | 1 and 2 | Cars, vans, utes and motorbikes, with or without a trailer or caravan |
| Rigid trucks | 3 to 5 | Two-, three- and four-axle trucks and buses |
| Articulated trucks | 6 to 9 | Semi-trailers with three to six axles |
| B-doubles and road trains | 10 to 12 | B-doubles, double and triple road trains |
Traffic by hour
TMR also publishes each site's average traffic for every hour of every day of the week, in each direction, with weekday and weekend averages. That's where you find the peak hour, and when traffic is quiet enough for works.
How traffic management uses AADT
- Queue lengths: QGTTM Part 3 estimates the end of queue at a stop/slow or portable signal site from a five-minute count, which can be worked out from the busiest hour of the hourly figures divided by 12, split by the heavy vehicle percentage. See QGTTM Part 3 queue length calculation.
- Sign duplication: QGTTM Part 3 asks for signs on both sides of the road on high-volume roads, 7,500 vehicles a day or more, as well as on all multilane roads.
- Work hours and methods: the hourly profile shows when a lane closure or stop/slow will cause the least delay, and when it needs to be avoided.
- Plans and permits: traffic management plans and permit applications often ask for traffic volumes to justify the treatment chosen.
Outside traffic management, AADT feeds pavement design (especially the heavy vehicle numbers), crash rate calculations, intersection design and planning for upgrades.
Finding the AADT for a road
TMR's traffic census is free on the Queensland Open Data Portal, with each year's counts back to 2004, and its hourly data back to 2010. The files are large spreadsheets keyed by road section, site and through distance, so finding the right site for a spot takes some matching.
Chainage does the matching for you. Look up any point on a state-controlled road and the chainage card shows the AADT and heavy vehicle percentage from the count site whose segment covers it, in your carriageway's direction on a divided road. Tap the figure to see the count site on the map with the stretch it stands for; tap the site for its counts each way, its vehicle classes, its counts by year (counted or estimated) and its traffic by hour of the day.
Frequently asked questions
What does AADT stand for?
Annual average daily traffic: the number of vehicles passing a point on a road in a day, averaged over a calendar year.
Is AADT both directions?
Usually, unless it says otherwise. TMR's traffic census gives AADT for both directions together and for each direction separately (with and against the road's gazettal direction).
How often is AADT counted?
Permanent sites count continuously. Coverage sites are counted for a short period every few years, and TMR estimates their AADT for the years in between. The census shows the year each figure was collected.
What is a high AADT?
It depends on the road. Busy urban motorways carry over 100,000 vehicles a day, the Bruce Highway near Yandina about 41,600, and remote highways a few hundred. For signage, QGTTM treats 7,500 vehicles a day or more as high volume.
What counts as a heavy vehicle in AADT?
Austroads vehicle classes 3 to 12: rigid trucks, buses, articulated trucks, B-doubles and road trains. Cars, vans and utes, including those towing, are light vehicles.
Sources
- Queensland Government Open Data Portal, Traffic census for the Queensland state-declared road network, including its field descriptions.
- Queensland Government Open Data Portal, Queensland traffic data averaged by hour of day and day of week.
- Queensland Department of Transport and Main Roads, Queensland Guide to Temporary Traffic Management Part 3 (November 2025), Sections 2.5.3 and 4.8.
- Austroads, Vehicle Classification System (12-bin), as used in TMR's traffic census.